This invention relates to lasers, and more particularly to a haolgenated or deuterated tetrazole suitable for use as a fuel to generate a laser of the gas dynamic transfer chemical type.
Laser is an acronym for light amplifications by stimulated emission of radiation. A laser produces a beam in the spectral region broadly defined as optical. The laser beam is coherent electromagnetic radiation having a particular well defined frequency. Coherence is a unique feature of the laser because the optical range which includes the near ultraviolet, the visible, and infrared wave lengths is incoherent. So ordinary light is incoherent while lasers are coherent. Because of coherence, lasers have extremely small divergence and are highly directional. Also enormous power is generated in a very small wavelength range. This power can be focused on a spot having a diameter of the wavelength itself, and is capable of producing from a 50 kilowatt outburst a radiant power density of 10.sup.12 watts per square centimeter which is about 10.sup.8 times the power density at the surface of the sun. Such power has many uses such as testing materials, welding, drilling or military applications. Because of the power produced, much research has been directed to the laser field.
There are two basic types of lasers known as the solid state laser and the gas laser. The solid state laser has a low energy when compared to the gas laser, because it produces a laser beam by electronic excitation of crystalline materials and is a rather complex system, as exemplified by the ruby laser. Due to the lower energy, coherence is an important feature of the laser beam produced in the solid state laser. Gas lasers, on the other hand, have such relatively high energy that coherence is neither achieved as well nor made as important in the lower energy solid state laser.
There are three basic types of gas lasers. Electric discharge, gas dynamic, and chemical lasers are known types of gas lasers. The basic physical process common to them is the competition between stimulated emission and absorption of monochromatic radiation, where the radiation energy corresponds to the difference between two distinct energy levels of an atomic or molecular system. In chemical lasers, the products of highly energetic chemical reactions are formed directly in vibrationally or electrically excited states with the upper levels preferentially populated. In gas dynamic lasers, an initially hot gas in thermodynamic equilibrium is rapidly expanded through a supersonic nozzle, and an inversion is formed by differential relaxation processes in the non equilibrium nozzle flow. In electric discharge lasers, the upper energy level is preferentially populated by collisions with electrons within a gas mixture energized by an electric field.
The laser effect in electric discharge lasers is produced by funneling the gas through an electric field to achieve the desired excited level and produce a laser beam. High energy levels are required to excite the gas to laser producing levels.
Chemical lasers depend on a carefully monitored flow of gases which intersect at precisely the right point at the precise angle with the desired velocity at the right temperature to react to produce the desired laser characteristics. These parameters are only a few of the parameters which must be controlled in order for a chemical laser to function. Controls on each of the parameters are highly complicated in themselves and must be integrated with other complicated controls to produce the laser beam. All of these complications substantially affect the use of the chemical laser.
Simplest of the three types of lasers to use is the thermal or gas dynamic laser. This laser produces the laser beam by means of a rapid gas expansion. This type of laser is simplest to handle because the reactants are generally solid or liquid and easier to handle and store. However, finding reactants to produce laser action is difficult.
Laser action occurs when two conditions are met: (1) population inversion is achieved and (2) avalanche process of photon amplification is established in a suitable cavity. Population inversion is established in an atomic system having at least one ground level, and at least two excited levels wherein one of the excited levels has a longer spontaneous emission lifetime than the other excited level. Inversion permits stimulated emission to exceed absorbtion which results in photon amplification. A more thorough discussion of laser action is found in U.S. Pat. No. 3,543,179 to Wilson incorporated herein by reference.
In spite of the difficulties involved in achieving a laser beam, the power of the laser beam renders the field highly fertile for research. Some of the areas most fertile are those which simplify the generation of a laser beam. The above-mentioned electrical discharge lasers, chemical lasers, and gas dynamic lasers are highly complex means of generating the desired laser beam. Efforts in the thermal laser field are made because of the simple operation. However, thermal generation of a laser beam is difficult. Chemical gas generation is a well-known method of simplifying a gas laser-generation process. The problem now becomes selecting an appropriate fuel or chemical which produces the proper gas for rapid thermal expansion when reacted or burned.
It is possible to pump gas dynamic lasers by use of hydrocarbon/air mixtures. These mixtures are ignited in a combustion chamber and then allowed to expand through a supersonic nozzle so that population inversion occurs. Theoretically, the efficiency of the laser increases with increasing combustion pressure and temperature, and with increasing expansion ratio. The combustion products must contain a high percentage of nitrogen, and approximately 10% to 15% carbon dioxide, and some percentage of water vapor. In addition, the combustion products should not contain any solid particles or highly corrosive gases; however, gases such as carbon monoxide and oxygen do not seem to be detrimental to the optical gain. These requirements rule out the use of conventional explosives such as trinitrotoluene, nitrocellulose, and the like, as well as double-base and composite propellants. For military applications, lasers must meet rigid requirements such as safety, storage, handling, and non-toxicity.
Additionally, for military applications, only solid propellants are considered to generate the laser gases mentioned above. The propellant would consist of only the elements carbon, hydrogen, oxygen, and nitrogen. However, solid organic compounds that can produce high nitrogen, low carbon dioxide and water upon burning are usually unstable, toxic, and hard to store, especially in large quantities. They also have high combustion temperatures that are difficult to use with laser equipment.
Gas dynamic and chemical lasers are similar in that both depend upon competition between stimulated emission and radiationless relaxation processes. Several publications have described the operation of gas dynamic lasers by the combustion of fuel-oxidizer mixtures in a combustion chamber. The hot gases in thermal equilibrium are allowed to expand through a supersonic nozzle so that population inversion occurs. The inverted N.sub.2 pumps the CO.sub.2.
One disadvantage of the N.sub.2 --CO.sub.2 --He GDL is that 60% He with 30% N.sub.2 is required for maximum power. Helium acts as a diluent and a relaxant for the CO.sub.2 lower laser level. The replacement of He with a more efficient relaxor such as 1% H.sub.2 O allows more N.sub.2 for pumping. The 89% N.sub.2 -- 10% CO.sub.2 -- 1% H.sub.2 O system which is one of the best, has the disadvantage of being virtually impossible to generate by the combustion of a non-gaseous fuel and oxidizer. At the present time, most GDLs depend upon bottle or cryogenic gases which is highly complicated.
Continuous wave operation at 10.6 in HCl--CO.sub.2, HBr--CO.sub.2, DF--CO.sub.2 and HF--CO.sub.2 chemical lasers are known. The laser emission is believed to be the result of upper CO.sub.2 laser level pumped by vibrational-rotational energy transferred from excited HCl, HBr, DF and HF molecules formed by chemical reactions.
In the DF-CO.sub.2 system, F. (provided by partial dissociation of F.sub.2 by photolysis, thermolysis, reaction of F.sub.2 with NO. or thermal dissociation of SF.sub.6 or NF.sub.3) is mixed with CO.sub.2, N.sub.2 and D.sub.2. The rapid and efficient chain reactions, F. + D.sub.2 .fwdarw. DF* + D. and D. + F.sub.2 .fwdarw. DF* + F. are driven to completion as the mixtures flows along a Teflon reaction tube.
The present chemical laser fuels have a disadvantage in that generation of halogen radicals by thermolysis or photolysis requires the addition of extra equipment such as furnaces or flash lamps.